1. Field of the Invention
The present invention relates to a component part of an automotive vehicle component part which is in sliding contact with another part in vehicle operation, and more particularly to a rocker arm of a valve operating mechanism of the automotive internal combustion engine which rocker arm is in sliding contact with a camshaft with a high bearing pressure.
2. Description of the Prior Art
Recently in the field of automotive internal combustion engines, performance improvement and freedom from maintenance have been rapidly and increasingly developed requiring more severe or improved slide-move characteristics or performance for component parts in sliding contact with other parts, for example, a rocker arm in sliding contact with a camshaft. In this regard, it has been proposed and put into practical use that the rocker arm is constructed of a rocker arm main body and a rocker arm tip in contact with the camshaft, in which the rocker arm tip is made of a variety of materials such as chilled casting, ferrous sintered alloy of the type wherein carbide is dispersed therein, super hard alloy, ceramic, and the like.
Of these materials, the chilled casting and the carbide dispersed type ferrous sintered alloy are presently insufficient in wear resistance. The super hard alloy is high in attacking ability against an opposite member (such as the camshaft). The ceramic is high in cost and liable to break down or fall off. Thus, such conventional materials are all insufficient in slide-move characteristics or performance required for the parts in sliding contact such as the rocker arm. Accordingly, it has been eagerly required to develop a rocker arm having a rocker arm tip which is lower in cost than the super hard alloy and the ceramic and exhibiting excellent wear resistance and low attacking ability againt the opposite member.